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‘Sensing Skin’ Gives Advance Warning of Structural Damage

06/30/2014

A team of researchers from North Carolina State University and the University of Eastern Finland have developed a new technology that could serve as an advance warning system to alert engineers of damage to concrete structures.

The “sensing” skin technology is an electrically conductive coat of paint made from copper or other similar materials that can be applied to either new or existing structures.

America’s infrastructure continues to age even as the necessary funds for its increasingly expensive upkeep are diverted to other projects. The latest infrastructure report card, which ranks structures like the nation’s dams, roads, airports, ports and railways, awarded the majority of these a D rating. Often, structural issues are fixed only after they become a major enough problem, affecting both commuters and utility providers, among others. In the face of this problem, scientists are turning increasingly towards new technologies that could help extend the life of current infrastructure.

“The sensing skin [technology] could be used for a wide range of structures, but the impetus for the work was to help ensure the integrity of critical infrastructure such as nuclear waste storage facilities,” Mohammad Pour-Ghaz, Ph.D., an assistant professor of civil, construction and environmental engineering at NC State and co-author of a paper describing the work published in Smart Materials and Structures, said.

The sensing skin is painted over a series of electrodes that are applied previously around the perimeter of a structure. A computer program runs a small current between arbitrary pairings of electrodes and records the electrical potential of each electrode. This data is used to calculate and monitor the sensing skin’s spatially distributed electrical conductivity; a decrease in the skin’s conductivity indicates that the structure has been damaged. A suit of algorithms developed by the researchers assists with identifying damage and its location on the structure.

“Determining the location of the damage based on the measured electrode potentials is a challenging mathematical problem,” Aku Seppänen, an Academy Research Fellow in the Department of Applied Physics at the University of Eastern Finland and co-author of the paper, said. “We had to develop new computational methods to more reliably determine where the damage is. Ultimately, I think our work represents an advance over previous algorithms in terms of accuracy.”

The researchers have thus far demonstrated the sensing skin’s ability on a small scale, using concrete beams measuring less than a meter wide. Their next step is to test the technology on a bigger scale.

“We want to show that this will work on real-world structures,” Pour-Ghaz said.